On the electromagnetic pulse produced by nuclear explosions

The electromagnetic pulse (EMP) produced by the gamma rays from nuclear explosions is discussed. The gamma rays produce a current of Compton recoil electrons, and these electrons produce further ionization so that the air becomes conducting. The Compton current leads to the generation of electromagnetic fields according to Maxwell's equations. The conductivity tends to limit the magnitude of the fields. Approximate methods of solving the equations are described by considering time regimes in which various terms in the equations are negligible, e.g., either the conduction current or the displacement current can be dropped. Further advantage is obtained by replacing the transverse fields by outgoing and ingoing waves; outgoing waves are dominant at early times. Features of the solutions are described for nuclear bursts at the ground surface and at high altitude. The history of EMP is reviewed briefly.